我正在为学校开发一个c ++项目，它是一个计算器程序，它接受一个中缀表达式并将其转换为后缀，然后简化表达式，避免浮点数。当我创建一个指向某个子类对象的超类（Expression）的指针（例如Addition）时，我遇到的问题是main，它无法找到构造函数。请让我知道我做错了什么。这是我第一次发帖。谢谢！
（编辑） 我正在使用codeblocks项目。它似乎不是链接器错误。
main.cpp中：
#include "InfixToPostfix.h"
#include "Expression.h"
#include "Addition.h"
#include "Subtraction.h"
#include "Multiplication.h"
#include "Division.h"
#include "Exponentiation.h"
#include "NthRoot.h"
#include "Logarithm.h"
#include "Integer.h"
#include <iostream>
#include <sstream>
#include <stack>
#include <limits>
#include <string>
#include <vector>
#include <typeinfo>
using namespace std;
Expression* createExp(char a){
if(a == '+'){
Addition addObj; //////////// This is where the error is,
Expression* addExp = &addObj; // I have tried a few ways...
// addObj = new Addition;
return addExp;
}else if(a == '-'){
Subtraction* subObj;
// subObj = new Subtraction;
return subObj;
}else if(a == '*'){
Multiplication* mulObj;
// mulObj = new Multiplication;
return mulObj;
}else if(a == '/'){
Multiplication* divObj;
// divObj = new Division;
return divObj;
}else if(a == '^'){
Exponentiation* expObj;
// expObj = new Exponentiation;
return expObj;
// }else if(a == "rt"){
// return new NthRoot();
// }else if(a == "log"){
// return new Logarithm();
}else{
Integer* intObj;
// intObj = new Integer;
int b = a-48; // convert to int
intObj->setValue(b);
return intObj;
}
}
int main()
{
InfixToPostfix object;
string postFix = object.convert();
cout << postFix;
Expression* root = createExp(postFix[postFix.length() - 1]);
Expression* currentNode = root;
Expression* nextNode;
int c = postFix.length() - 2; // second from last
while(c >= 0)
{
if(postFix[c] == ' '){
c--;
}else{
nextNode = createExp(postFix[c]);
if(typeid(currentNode) == typeid(Integer)){
}
if(currentNode->getRightSide() != 0)
{
currentNode->rightSide = nextNode;
currentNode = nextNode;
}else if(currentNode->getLeftSide() != 0)
{
currentNode->leftSide = nextNode;
currentNode = nextNode;
}
}
c--;
}
cout << root->getValue();
return 0;
}
Expression.h：
#ifndef EXPRESSION_H_INCLUDED
#define EXPRESSION_H_INCLUDED
#include <iostream>
#include <sstream>
#include <stack>
#include <limits>
#include <string>
#include <vector>
using namespace std;
class Expression
{
private:
protected:
int value;
public:
Expression();
virtual ~Expression()=0;
virtual void setValue(int b)=0;
virtual int getValue()=0;
Expression* leftSide;
Expression* rightSide;
virtual Expression* getLeftSide()=0;
virtual Expression* getRightSide()=0;
virtual vector<Expression*> getNumeratorFactors()=0;
virtual vector<Expression*> getDenominatorFactors()=0;
virtual vector<Expression*> getAdditiveTerms()=0;
virtual Expression* simplify()=0;
};
#endif // EXPRESSION_H_INCLUDED
Expression.cpp：
#include "Expression.h"
#include <iostream>
#include <sstream>
#include <stack>
#include <limits>
#include <string>
#include <vector>
using namespace std;
Expression :: Expression()
{
LeftSide = 0;
RightSide = 0;
}
Expression :: ~Expression()
{
}
Addition.h：
#ifndef ADDITION_H_INCLUDED
#define ADDITION_H_INCLUDED
#include "Expression.h"
#include <iostream>
#include <sstream>
#include <stack>
#include <limits>
#include <string>
#include <vector>
using namespace std;
class Addition: public Expression
{
private:
int value;
public:
Addition();
~Addition();
virtual void setValue(int b);
virtual int getValue();
Expression* leftSide;
Expression* rightSide;
virtual Expression* getLeftSide();
virtual Expression* getRightSide();
virtual vector<Expression*> getNumeratorFactors();
virtual vector<Expression*> getDenominatorFactors();
virtual vector<Expression*> getAdditiveTerms();
virtual Expression* simplify();
};
#endif // ADDITION_H_INCLUDED
Addition.cpp：
#include "Addition.h"
#include <iostream>
#include <sstream>
#include <stack>
#include <limits>
#include <string>
#include <vector>
using namespace std;
Addition::Addition()
{
leftSide = 0;
rightSide = 0;
setValue(int b)=0;
getValue()=0;
getLeftSide()=0;
getRightSide()=0;
getNumeratorFactors()=0;
getDenominatorFactors()=0;
getAdditiveTerms()=0;
simplify()=0;
}
Addition :: ~Addition()
{
}
virtual int Addition :: getValue()
{
return getLeftSide().getValue() + getRightSide().getValue();
}
virtual Expression* Addtion :: getLeftSide()
{
return leftSide;
}
virtual Expression* Addtion :: getRightSide()
{
return rightSide;
}
virtual vector<Expression*> Additon :: getNumeratorFactor()
{
}
virtual vector<Expression*> Additon :: getDenominatorFactor()
{
}
virtual vector<Expression*> Additon :: getAdditiveTerms()
{
}
virtual Expression* Additon :: simplify()
{
return getLeftSide() + getRightSide();
}